Suspension and drive mechanism for a multi-surface vehicle

ABSTRACT

A tracked vehicle produces a pressure no more than 3 psi on the ground by increasing the number of contact points on the inner surface of the track. The stiffness of the track is also selected to minimize bowing between the idler wheels or rollers. The track is therefore kept substantially straight between the rollers so increase the efficiency associated with transferring power to track. The drive sprocket is positioned above the ground so as to eliminate complexity in the design and yet effectively transmit power to the tracks. Positioning the drive sprocket above ground also prevents derailing of the track. The track is also held in a constant state of tension on the driver sprocket and the roller. This too prevents derailment. The undercarriage of the vehicle includes torsion axles and sealed bearings to provide for a lower maintenance track. Components associated with the undercarriage do not require constant greasing and cleaning of the idler wheels. The track is beveled so that it does not rip up surfaces. The drive sprocket is provided with roller sleeves that accommodate the changes in the pitch line of an elastomeric flat track. The sprocket does not “scrub” the areas between the driving lugs. The drive sprocket includes a pair of scrapers and a pair of conical shields which provide self cleaning and which remove debris from the sprocket area.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.09/063,685, filed on Apr. 21, 1998, the specification of which isincorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to a multi-surface vehicle, and more particularlyto the suspension and drive mechanism associated with a multi-surfacevehicle with a rubber track.

BACKGROUND OF THE INVENTION

A variety of track driven vehicles have been around for many years.Tracked vehicles vary from 100 ton military tanks and bull-dozers to 300pound snowmobiles. Track types vary from segmented steel tracks to onepiece molded rubber tracks.

One of the major design challenges with all types of tracks and vehiclesis to find the most efficient way to transfer the torque of the drivemechanism to the track with minimum power loss. There are many torquetransmission systems. The three most common torque transmission systemsare an external drive, a friction drive and an internal drive. Externaldrives include a sprocket with a fixed number of teeth around thecircumference that drives against a rigid member attached to the track.The sprocket teeth protrude through the track to a point where the rigidmembers can not slip back under a heavy load. Friction drives include awheel attached to the drive axle and drive against the inside surface ofa track. The outside of the wheel and the inside of the track aretypically made of resilient material such as rubber or other composites.The track tension must be extremely tight to prevent slippage. The tracktension also results in power loss. Internal drive systems, also knownas involute drives, have a track with drive lugs attached to the insidesurface of the track. The drive lugs may be molded to the inside surfaceof a rubber track. The drive sprocket is made by attaching rigid driveteeth to a rigid radius wheel. The sprocket teeth drive against theinternal drive lugs on the track.

Internal drive systems are generally considered the most efficient drivefor tracks made of elastomeric material such as rubber when the drivelugs and drive sprockets are properly matched. They are properly matchedwhen the pitch diameter of the sprocket matches the pitch line of thetrack. Another way of determining whether they are properly matched iswhen the pitch diameter of the sprocket causes the drive teeth to matchperfectly with the center to center distance between the track drivelugs. In practice, proper matching is difficult to achieve especiallywhen using an elastomeric or rubber track. Tracks made of elastomericmaterials are resilient. As a result, the elastomeric material stretchesor contracts slightly depending on a number of factors. One of the morecommon factors that causes changes in the pitch length is the variationin the load applied to a track during operation of the multi-surfacevehicle. The load on the track and on the internal lugs will be higherwhen the vehicle is pulling a log as compared to the load on the trackapplied to merely move the vehicle over terrain. The tracks may beloaded differently when turning. An outside track will typically beloaded to a higher degree when compared to an inside track. The pitchlength of the track varies with the variations in the load applied tothe track.

Variations in the pitch length of the track results in a mismatchbetween the pitch length of the track and the pitch diameter of thesprocket. When using a sprocket having rigid drive teeth, the change inthe pitch length along the track causes the sprocket teeth to “scrub in”or “scrub out” or both. In other words, the rigid tooth is rubbingbetween the individual drive lugs on the internal surface of the flatbelt. This causes a loss in efficiency. Scrubbing in or out can resultin extreme power loss and excessive wear on the track drive lugs andsprocket teeth.

Another common problem with flat tracks such as those made from anelastomeric material is that foreign matter or sticky material builds upin the sprocket area. Metal tracks usually have openings through whichat least some foreign matter may be passed. The buildup is worse on aflat track. When foreign matter builds up in the sprocket area the pitchdiameter or the pitch line of the flat track is likely to change. Thisresults in power loss and excessive wear. Rocks, sticks, grass, mud,snow and other materials may build up in the sprocket area.

Military tanks and bull-dozers are two common vehicles featuring metaltracks. Metal tracks are typically mounted on drive wheels and idlerwheels that are mounted on springs or suspension systems that allow thedrive wheel to move slightly from a fixed position. The use of rollerson the track drive segments of a metal track reduces noise and reduceswear between the individual segments of the metal track. The springs orsuspension associated with the idler wheels allows the metal track toaccommodate obstacles encountered by the metal track. At the drivewheels, the springs also accommodate slight variations in pitchdiameter.

Metal tracked vehicles have many problems. One of the problems is thatmetal tracked vehicles are very heavy and tend to sink in and damagerelatively soft surfaces. The pressure produced by a metal trackedvehicle is relatively high. For example, when a metal tracked vehicleoperates in mud, the vehicle typically sinks to solid ground rather thanpassing over such a surface. The tracks also are tough on surfaces suchas grass or lawns. The pressure produced by the metal track of abull-dozer or a tank typically produces indentations in a surface. Forexample, if a bull-dozer passes over a residential lawn, the pressure ishigh enough to compact the earth and form a permanent indentation. Ahome owner would have to fill in the impressions with additional soil tofix the lawn. In addition, the metal tracks typically have square edgeswhich dig into surfaces during turns. A turning bull-dozer would rechavoc with residential lawns. Metal tracks can also become derailed.

Some tracked vehicles have used rubber tracks. Typically, designers ofmetal tracked vehicles carry over many of the design characteristicsinto flat track vehicles using elastomeric or rubber tracks. Many of theproblems encountered with metal tracks are also encountered with rubbertracks. For example, many rubber track designs include a track mountedon drive wheels or sprockets which are spring mounted. The problem ofmatching the pitch line of the track to the pitch diameter of thesprocket is further exacerbated. The drive wheels do not maintain thetrack near a constant state of tension so the pitch line can fluctuatewidely.

In addition, the drive sprocket is positioned so that it in contact withthe surface. Typically, the drive sprocket will be at the rear of thevehicle and positioned so that the track passes between the drive wheeland the ground. In such designs, the rear drive wheel has two jobs. Therear drive wheel drives the track and maintains the alignment of thetrack. When the rear drive wheel is on the ground, the two jobs the reardrive wheel is called on to do work against one another. When driven,the track tends to want to leave the drive wheel or “jump off thesprocket”. It is necessary to maintain alignment to prevent derailing.Rear drive wheels on the ground are more prone to derailing since theforces associated with doing the two jobs counteract one another.Another problem with rear drive wheels on the ground is that they tendto require additional complexity. Elongated gear boxes must be used totransfer power to these rear on the ground drive wheels.

Another problem associated with flat elastomeric tracked vehicles isthat there are few idler wheels that contact the ground. The track tendsto bow between the idler wheels which results in a loss of traction. Inaddition, with fewer points on the ground and bowing between the wheels,the effective surface pressure at various points under the wheels ishigh. The tracked vehicle does not have an even pressure across the flattrack. Still another problem is that these vehicles are highmaintenance. Each individual wheel must be greased periodically. Inaddition, since the environment for use includes foreign matter such asdirt, the individual idler wheels tend to wear. Because of the highmaintenance and cost, there is a tendency to use lesser numbers ofwheels in various designs.

As a result of high pressure per wheel, most designs of tracked vehiclesusing elastomeric or steel tracks are not environmentally friendly.Current designs still indent soft surfaces and tear up grass lands. Inaddition, the current vehicles are high maintenance. High maintenance isneeded to assure that the components of the undercarriage do notprematurely wear.

Thus, there is a need for a for a tracked vehicle that produces a lowpressure on the surface and which is environmentally friendly. Inaddition, there is a need for a lower maintenance vehicle not prone toderailing the track. In addition, there is a need for a vehicle whichhas many contact points, and therefore has lower pressure per wheel, onthe track as it passes over the surface. There is also a need for avehicle which does not require constant greasing and cleaning of thewheels in contact with the track. There is also a need for a vehiclewhich places the drive sprocket off the ground so as to eliminatecomplexity in the design and yet effectively transmit power to thetracks. In addition, there is a need for a sprocket which willaccommodate the changes in the pitch line of an elastomeric flat track.In addition, there is a need for a sprocket which will not “scrub”between the driving lugs. There is also a need for a sprocket which isself cleaning and which removes debris from the sprocket area tominimize problems associated with debris build up changing the pitchrelationship between the sprocket and the flat track.

SUMMARY OF THE INVENTION

A tracked vehicle produces a pressure no more than 3 psi on the groundand less than 190 pounds per contact point on the inner surface of thetrack. Multiple wheels across the width of the track eliminate bowingbetween the idler wheels or rollers. The track is therefore keptsubstantially straight across the rollers to increase the efficiencyassociated with transferring power to track. The drive sprocket ispositioned above the ground so as to eliminate complexity in the designand yet effectively transmit power to the tracks. Positioning the drivesprocket above ground also prevents derailing of the track. The track isalso held in a constant state of tension on the driver sprocket and theroller. This too prevents derailment. The undercarriage of the vehicleincludes torsion axles and sealed bearings to provide for a lowermaintenance track. Components associated with the undercarriage do notrequire constant greasing and cleaning of the idler wheels. The track isbeveled so that it does not rip up surfaces. The drive sprocket isprovided with roller sleeves that accommodate the changes in the pitchline of an elastomeric flat track. The sprocket does not “scrub” theareas between the driving lugs. The drive sprocket includes a pair ofscrapers which provide self cleaning and which remove debris from thesprocket area.

Advantageously, the vehicle will travel over soft surfaces withoutcausing damage to the surface. In addition, unlike other vehicles, thevehicle sinks little in soft mud or snow. The resulting vehicle is veryeffective in transmitting power to the surface over which it passes. Thevehicle requires very low maintenance since the bearings associated withthe undercarriage are sealed. Other suspension units are simple andstraightforward and require little or no maintenance. The vehicle alsois less prone to track derailment.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of the preferred embodiments can bestbe understood when read in conjunction with the following drawings, inwhich:

FIG. 1 is a side view of the multi-surface vehicle.

FIG. 2 is perspective view of the undercarriage of the multi-surfacevehicle.

FIG. 3 is perspective view of the rubber track used with themulti-surface vehicle.

FIG. 4 is a top view of the track showing the tread pattern.

FIG. 5 is a cross-sectional view along line 5—5 in FIG. 4.

FIG. 6 is a cross-sectional view along line 6—6 in FIG. 4 showing theidler wheels in phantom engaging the lugs of the track.

FIG. 7 is an exploded perspective view showing multiple wheels attachedto a single tubular axle having multiple wheels and sealed bearings.

FIG. 8 is a perspective view of an axle 710 and the wheel plate.

FIG. 9 is a perspective view of the drive sprocket which engages thedrive lugs on the track and a scraper.

FIG. 10 is a cross-sectional view showing the suspension unit, alsocalled the rear torsion axle and swing joint.

FIG. 11 is a partial perspective view of the undercarriage of themulti-surface vehicle as it engages an obstacle on the surface beingtraversed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings which form a part hereof,and in which are shown by way of illustration specific embodiments inwhich the invention may be practiced. It is to be understood that otherembodiments may be utilized and structural changes may be made withoutdeparting from the scope of the present invention.

FIG. 1 shows a perspective view of a multi-surface vehicle 100 on asurface 110. The multi-surface vehicle 100 includes a frame 102 whichcarries an engine 120 such as an eighty horsepower, 4.5 liter John DeerePowerTech Diesel or a one hundred fifteen horsepower, 4.5 liter JohnDeere PowerTech Turbo Diesel. Both of these engines are available fromJohn Deere and Company of Moline, Ill. The engine 120 powers ahydrostatic transmission which powers hydraulic drive motors withplanetary gear boxes which eliminates additional chains and sprockets,thereby lessening the complexity and increasing the efficiency of thedrive system. Two auxiliary pumps are used to power differentaccessories. As shown, the vehicle includes a loader/bucket accessory130. The engine 120 powers hydraulic pumps used to drive the hydrauliccylinders 132 and 134 for operation of the loader 130. Otheraccessories, such as a blade or logging device may be substituted forthe loader 130. The vehicle 100 also includes an operator cab 140. Theoperator cab is equipped with controls for controlling the loader 130and for operating the multi-surface vehicle 100. Attached to the frame102 of the multi-surface vehicle 100 is an undercarriage 200. Aduplicate undercarriage is attached to the other side of the frame 102.The undercarriage 200 is attached to the frame 102 via torsion axle typesuspension units 1000. The undercarriage 200 includes a drive sprocket900 for driving a flat elastomeric or rubber track 300. It should benoted that the drive sprocket 900 is positioned off the surface 110 sothat it will stay clean for a longer life. The undercarriage 200features multiple idler wheels 700 on axles (shown in FIG. 2) whichengage the inner portion of the track 300 as the track engages thesurface 110. The wheels 700 are of a selected diameter and spaced sothat track 300 will not bow between the contact points as the tracktravels over the surface 110. The properties of the elastomeric track300 also are selected so that the track has a sufficient stiffness sothat the track 300 stays substantially straight between the contactpoints of the various idler wheels 700. As shown in FIG. 1, eightdifferent axles carrying wheels 700 are shown in contact with the track300. The wheels 700 provide multiple contact points which more evenlydistribute the weight of the vehicle 100 and its load over the twotracks 300. By keeping the individual tracks 300 substantially straightbetween the various contact points, the track 300 is also better able togrip the surface 110.

FIG. 2 is perspective view of one side of the undercarriage 200 of themulti-surface vehicle 100. The As can be seen from this view, there aretwo frame members 202 and 204 which are part of the frame 102 of thevehicle 100. The undercarriage 200 includes an undercarriage frame 210which includes an upper portion 212 and a side skirt 214. Attached tothe upper portion 212 of the undercarriage frame 210 are cross members220, 222, and 224. The cross members include a channel each of whichaccommodates a suspension unit or torsion axle 1000. The torsion axletype suspension unit 1000, which will be described in more detail inFIG. 9, provides an essentially maintenance free suspension member whichdoes not require greasing or regular cleaning. Attached to each end of across member is a wheel plate 230 and a wheel plate 232. The wheelplates for cross member 222 are described here. For the sake of clarity,the other wheel plates are not numbered. The other wheel plates areattached to cross members 220 and 224 are substantially identical to thewheel plates 230 and 232 attached to cross member 222. Each wheel platecarries two wheel axles 710 and 712. Each wheel axle carries threewheels 700. The wheels 700 have a rubber or plastic outer annulus 702attached to a central wheel 704 made of either plastic or metal. Theouter annulus provides for enhanced contact with the flat track or belt.The wheels 700 attached to first end axle 714 and to second end axle 718are fixed with respect to the undercarriage frame 210. The end axles 714and 718 are actually in a fixed position in a notch in the side skirt214 of the undercarriage frame 210.

Also attached to the undercarriage frame 210 at a position above the endaxle 718 is the drive sprocket 900. The drive sprocket 900 is in a fixedposition with respect to the undercarriage frame 210. It should be notedthat the wheels on the end axle 714, the wheels on the end axle 718, andthe drive sprocket 900 are all in fixed position with respect to theundercarriage frame 210. These particular wheels and the drive sprocket900 define the outer limits of the flat track 300. It is important tohave a fixed position for these wheels and the drive sprocket 900 sothat the elastomeric track 300 is held in a substantially constant stateof tension. The pitch length of an elastomeric track, such as those madeof rubber, will vary slightly. The pitch length will stretch slightly asvariable loads are applied to the track 300. The use of springs or othersuspension means at these points will allow for the track to collapseinward too much when a load is placed on the track 300. Springs or othersuspension means, commonly used to keep metal tracks, will allow theelastomer tracks to dislodge or come off. Therefore, it is imperativethat no springs or anything are used to maintain the tension on thetrack.

As can be seen, the wheels 700 provide for a plurality of contact pointsonto the internal surface of the track. In fact the eight axles eachhaving 3 wheels provide for a total of 24 contact points to the internalsurface of the flat track 300. The vehicle has a duplicate undercarriageon the other side of the vehicle. The end result is at any given timethere is approximately 2,844 square inches in contact with the ground orsurface 110. Forty eight wheels or contact rollers spread the weightevenly over the two tracks 300 so that superior traction and flotationare achieved. There is also a minimal amount of force at each contactpoint. The ground pressure associated with the vehicle 100 is no morethan 3 psi (pounds per square inch) which means that the vehicle has thecapability to work on soft ground or lawns without forming ruts orcompacting soil.

Of course to keep the soil from compacting or forming ruts, theelastomeric track 300 is formed of a material which is stiff enough suchthat it will not bow between the contact points of the wheels 700. Thisthe track 300 substantially flat and in contact with the ground orsurface 300.

FIG. 3 is perspective view of the elastomeric or rubber track 300 usedwith the multi-surface vehicle 100. The track 300 has an outer surface310 which has a tread pattern 312. The track 300 also has an innersurface 320. Attached or molded to the inner surface of the track 300are a plurality of drive lugs 322. The drive lugs 322 are arranged intwo rows 330 and 332. The spacing between the rows 330 and 332 isselected so that the width of the middle wheels on a three wheel axlefits between the first row 330 of drive lugs 322 and the second row 332of drive lugs 322. Typically approximately one-half inch of clearance isprovided so that the track 300 can shift an appropriate amount during aturn or other operation. The outer wheels 700 fit between one row oflugs 322 and the outer edge of the track 300. The spacing from one lug322 to another within a row is selected so that the lugs 322 willproperly engage the sprocket 900. Proper engagement would match thepitch diameter of the drive sprocket 900 to the pitch line of the track300. Of course, this is difficult to achieve since there are differentforces on the track 300 at various times.

FIG. 4 is a top view of the outer surface 310 of a section of the track300 showing the tread pattern 312. The tread patten 312 includes aseries of transverse grooves 340, 341, 342, 343, and 344. The treadpattern 312 also includes a first beveled edge 314 and a second bevelededge 316. The beveled edges 314 and 316 allow some side-to-side movementwhich accommodates turns made with the elastomeric or rubber track 300.The allowance of the side-to-side motion from turning makes for a veryenvironmentally friendly track. Unlike square tracks that typically diginto the ground and produce track damage, the beveled edges 314 and 316on the track 300 can slip over the ground during a turn to leave theterrain substantially undamaged. The transverse grooves 340, 341, 342,343, and 344 are at a selected spacing and at a selected depth so as toleave ribs between the grooves. The ribs formed between the grooves 340,341, 342, 343, and 344 are dimension so that after the track passes overthe wheels 700 associated with the end axle 714 and into contact withthe ground, the ribs close and grip the vegetation or the ground surface110 for added traction.

FIG. 5 is a cross-sectional view along line 5—5 in FIG. 4. Both theinner surface 320 and the outer surface 310 of the track are shown inthis view. The track also includes stiffeners 350, 352, and 354. Thestiffeners 350, 352 and 354 increase the stiffeners of the track 300across the width of the track 300. The stiffeners 350, 352 and 354 arefiberglass rods which are molded into the track. The stiffeners 350, 352and 354 are placed in the wider ribs such as those formed betweengrooves 341 and 342, and formed between grooves 343 and 344. The drivinglugs 322 are shown molded or attached to the inner surface 320 of thetrack 300. The distance between the lugs 322, depicted by the referencenumber 360 is selected so that the engaging portions of the drivesprocket 900 engages the portion of the inner surface 320 betweenadjacent lugs 322 in a row. Ideally, the “teeth” of the drive sprocket322 would engage the lugs 322 with little or no backlash or extraspacing located between the lugs 322. This is difficult to achieve giventhat the pitch of the elastomeric track 300 will stretch slightly as afunction of the load placed on the track 300.

FIG. 6 is a cross-sectional view along line 6—6 in FIG. 4. The rollersor idler wheels 700 engaging the lugs of the track have been added inphantom to FIG. 6. As can be seen, the rollers or idler wheels 700 donot fit tightly with respect to the rows 330 and 332 of lugs 322. Thisallows for slight movement of the track with respect to the wheels 700attached to a single axle, such as axle 710 (shown in FIGS. 2 and 7).The rows 330 and 332 are spaced such that the wheels 700 of theundercarriage fit between the rows 330 and 332. The drive lugs 322 thusprevent the track from dislodging or jumping off since the engagingdrive lugs control or stop the side-to-side motion of the track 300. Thedrive lugs 322 have beveled sides 323 and 324 which allow the beveledsides of the multiple wheels to butt up against the tracks. Anotheraspect of these driving lugs 322 is that the spacing on them allows thetrack some lateral movement. The lateral movement enhances theturnability of the vehicle 100.

One stiffener 350 is shown in FIG. 6. The stiffener 350 is molded intothe track 300 and is a fiberglass rod positioned transverse to the pathof travel. The transverse fiberglass rods strengthen the track. Thefiberglass rod 350 terminates well short of the beveled edges 314 and316 so as to prevent the stiffener 350 from releasing from the flattrack 300. On other flat tracks, the release of a fiberglass rod fromthe track was a precursor to track failure. As a result, the fiberglassrod 350 is stopped well short of the end of track 300 and then envelopedin five to seven layers of Kevlar or another tire cording material. Thisprevents the stiffener 350 from leaving the flat track 300 therebyforming a weak spot in the track.

FIG. 7 is an exploded perspective view showing multiple flanges 720,721, 722, and 724 rotatably attached to a single tubular axle 710. FIG.8 shows an assembled axle and attached wheels. Now turning to FIGS. 7and 8, the idler wheels or rollers 700 are attached to a the flanges720, 721, 722 and 724. There are two types of rollers or idler wheels700. The first type of roller or idler wheel 700 is an outside wheel 702which fits one of the ends of the axle 710. The second type of roller oridler wheel 700 is an intermediate wheel 704. The intermediate wheel 704attaches to flanges 721 and 722 intermediate the two ends of the axle710. The intermediate wheel 704 comprises a first half 706 and a secondhalf 708. Each of the two halves 706 and 708 is split along a diameterof the wheel 704 to form two semicircular halves. The two semicircularhalves 706 and 708 are bolted to the flange 722 on the axle 710 to forman intermediate wheel 704. The outside wheels 702 and the intermediatewheel 704 form a circular plastic rim with a rubber outer diameter. Theplastic rims are bolted to the flanges 720, 721, 722, and 724. Theoutside wheels are provided with an endcap 732 and an endcap 734.

The axle 710 is a hollow tubular element. The flanges 720, 722, and 724are attached to the hollow tubular element. The axle 710 or hollowtubular element is mounted on a shaft 730. The shaft 730 has two endswhich protrude from the ends of the hollow tubular axle 710. The tubularaxle 710 is rotatably attached to the shaft 730 by a first rollerbearing set 750 and a second roller bearing set 752. The entire innerportion of the axle is filled with oil or grease. The roller bearings750 and 752 are both sealed bearings. The roller bearings 750 and 752are provided with multiple seals so that a sealed bearing for all threewheels 700 (shown in FIG. 8) is formed. Use of a sealed bearing sharplyreduces maintenance time and keeps the life of the bearings high.Including three rollers or idler wheels 700 on an axle 710 is lessexpensive to manufacture and also provides for a maintenance free partthat lasts up to the life of the vehicle 100. Each end is provided withthree seals. The bearing has a first seal 760, an annular plastic orrubber element that fits over one side of the bearings, which comes withthe bearing set. A second seal 762 is positioned outside of the bearingset. A third seal 764 includes seven different seals in one. The thirdseal 764 has a tortuous path to prevent dirt from getting into thebearing or into the space between the axle 710 and the shaft 730. Ifdirt or other contaminants get into the grease or the oil covering thebearing sets 750 and 752, the life of the bearings will be shortened.However, dirt entering through the first seal 760, the second seal 762and the third seal 764 would have to pass through nine seals in order toget to the lubricant. The rollers in each of the bearing sets are in acage. The roller cage and the bearings are submersed in the oil orgrease found within the hollow tubular axle 710.

FIG. 8 shows the wheels 700 attached to the tubular axle 710. The singleshaft 730 is shown protruding from the sealed end of the tubular axle710. The shaft 730 extends beyond the endcap 734. The shaft 730 includesa flat or keyway 740 that engages the wheel plate 230. The wheel plate230 includes an axle capture plate 231 which, when bolted to the wheelplate 230, captures the axle 730. Only one axle capture plate is shownin FIG. 8.

FIG. 9 is a perspective view of the drive mechanism including thesprocket 900 which engages the drive lugs 322 on the track 300. A firstscraper 940 and a second scraper 942 are positioned near the innerdiameter of the drive sprocket to clear the drive sprocket of debristhat may otherwise accumulate. The driver sprocket 900 includes acentral drive plate 902. A number of tubular elements 904 are welded orotherwise attached to the central drive plate 902. Attached to thecentral drive plate is a first annular unit 910 and a second annularunit 911. As shown, the first annular unit 910 and a second annular unit911 are attached to the central drive plate 902 using a long bolt or pin912. A set of spacers 914 and 916 are used to define the spatialrelationships between the central drive plate 902 and the first annularunit 910 and the second annular unit 911. Spacers 914 and 916 also carryroller sleeves 920 and 922. The roller sleeves roll with respect to thespacers and with respect to the central drive plate 902. In other words,the roller sleeves 920 and 922 fit between the drive plater 902 and thefirst annular unit 910, and and between the drive plater 902 and thesecond annular unit 911. The roller sleeves 920 and 922 are dimensionedand spaced so that they can engage the spaces between the drive lugs 322on the inside portion 320 of the rubber or elastomeric track 300. Theroller sleeves are advantageous in that they are self adjusting. As therubber track passes over a roller sleeve 920 and 922, the pitch of thetrack 300 actually changes since the track is elastomeric. The rollersleeves accommodate such changes in pitch since they can roll betweenthe drive lugs 322 rather than scrub the inner surface 320 between thedrive lugs 322. The end result is that the roller sleeves 920 and 922also prevent chatter or extra vibrations at various speeds of the track.

The drive plate 902 is attached to a sprocket driver 930. The sprocketdriver 930 is attached to portion of the frame of the vehicle and whichincludes a first scraper 940. Also attached to the sprocket driver 930is a hydraulic pump 932. The hydraulic pump is attached to a source ofhydraulic fluid. As hydraulic fluid is passed through the hydraulic pump932 an output shaft 934 turns a planetary transmission system housedwithin the sprocket driver 930. The central drive plate 902 is attachedto an annular ridge 909 on the sprocket driver 930. A second scraper 942is attached a plate 907 which is attached to the undercarriage frame210. The sprocket driver 930 is attached to the plate 907. There are aseries seals and a cap 905 that prevents contamination of the sprocketdriver 930 with dirt or other contaminants.

The scrapers 940 and 942 force and remove the debris from the drivesprocket 900 and deposit it outside the drive sprocket 900. This iscritical since build up of debris within the sprocket will generallytend to change the pitch line of the track further. In addition, debrisbuild up tends to act to dislodge or derail the track 300 from the drivesprocket 900. The first scraper 940 and the second scraper 942 arecantilevered in toward the central drive plate 902 of the drive sprocket900. The second scraper 942 is cantilevered from another plate 907 thatis typically attached to the undercarriage frame 210. The first scraper940 and the second scraper 942 are positioned near the inner diameter ofthe rollers 920 and 922 of the driver sprocket 900. The scrapers 940 and942 remove debris from the rollers and force the debris away from thesprocket driver 930 and the track 310. The scrapers 940 and 942 arecantilevered and stick into the inside diameter of the driver sprocket900. Without the scrapers 940 and 942, mud and other debris wouldaccumulate and eventually lift the track 300 from the drive sprocket 900to dislodge it from its operating position. The scrapers 940 and 942 arearcuate in shape. By dislodging mud and other debris from the driversprocket 900 and placing the debris elsewhere, the scrapers 940 and 942keep the driver sprocket 900 clean and clear of mud or other debris.

The placement of the driver sprocket 900 enhances the ability of thetrack to stay on or not become dislodged, when compared to othervehicles. Now referring FIGS. 1, 2 and 9, the driver sprocket 900 isplaced off the ground or surface 110, and toward the rear of thevehicle. Placing the driver sprocket above the ground prevents derailingfor several reasons. The force of the driver sprocket 900 on the tracktends to act to dislodge the track 300 from the driver sprocket 900.When the driver is on the ground, not only is the driver sprocketdriving the track 300, it is also trying to maintain the alignment ofthe track. Thus, when the driver sprocket 900 is on the ground the twojobs counteract one another. In other words, the track is undergoing aforce tending to dislodge or derail the track 300 while also being usedto keep the track 300 aligned. Placing the driver sprocket 900 above theground removes the function of maintaining alignment. The above grounddriver sprocket's only function is to drive the track 300. In addition,placing the driver sprocket 900 above ground and near the rear of thevehicle prevents dislodgment of the track 300. In the elevated position,the driver sprocket applies a large force to the track at the last orrear axle carrying three roller or idler wheels 700. The drive sprocket900 pulls the track 300 into alignment with the wheels associated withthe rear axle thereby keeping the track from being dislodged or comingoff the rollers. It should be noted that dislodgement or track derailingis very costly and time consuming. Many times the track 300 is ruined ordamaged due as a result of being dislodged.

FIG. 10 is a cross-sectional view showing the axle mounting bracket 1010which uses a several suspension units also called a torsion axle 1000.Each torsion axle 1000 is comprised of a shell 1020 of a length ofsquare tubular material. An inner bar 1030 having a substantially squarecross section is positioned within the shell 1020. Rubber cords 1040 areplaced between the shell 1020 and the inner bar 1030. The inner bar isplaced on a diagonal with respect to the inside square cross section ofthe tubular material comprising the shell 1020. Within the squaretubular stock of the shell 1020, there is fitted a squarecross-sectional piece of rectangular stock referred to as the inner bar1030. The inner bar 1030 has a diagonal which is slightly less than theshortest dimension between the walls of the square tubular stock of theshell 1030. The inner bar 1030 makes a diamond inside or is fittedwithin the square tubular stock so that it looks like a diamond withinthe perimeter of the square tubular stock shell 1020. Positioned in thecorners of the square tubular stock of the shell 1020 are fourelastomeric cords or rubber cords 1040 which run the entire length ofthe shell 1020.

This arrangement provides for a stiff suspension unit or torsion axlethat never requires lubrication and is therefore maintenance free andvery reliable. The torsion axles 1000 are used throughout theundercarriage 200. Turning briefly to FIG. 2, the x's shown in thatfigure depict attachments which use the torsion axle 1000. For example,two wheel plates 230 and 232 carry two axles 710 and 712. Each of theaxles 710 and 712 have three wheels attached thereto. The wheel platesare attached to one another via a torsion axle 1000. The torsion axle1000 is a stiff suspension member used to attach two axles of threewheels a piece to the undercarriage frame 210. The end result is aninexpensive, simple, and straightforward suspension member that isimpervious to dirt, requires little or no maintenance, and which doesnot need to be sealed.

FIG. 11 is a partial perspective view of the undercarriage 200 of themulti-surface vehicle 100 as it engages an obstacle 1100 on the surface110 being traversed. The resulting amount of stiffness produced by thetorsion axles 1000 allows the wheels to hug the ground 110 even when arock or other obstacle 1100 is encountered so as to keep more tread 312of the track 300 on the ground 110 at any given time. When anobstruction is not encountered, the torsion axle 1100 is sufficientlystiff so that the belt or rubber track maintains a substantially unbowedstate between the wheels 700 associated with the undercarriage 200.

Advantageously, the vehicle will travel over soft surfaces withoutcausing damage to the surface. In addition, unlike other vehicles, thevehicle sinks little in soft mud or snow. The resulting vehicle is veryeffective in transmitting power to the surface over which it passes. Thevehicle requires very low maintenance since the bearings associated withthe undercarriage are sealed. Other suspension units are simple andstraightforward and require little or no maintenance. The vehicle alsois less prone to track derailment.

Although specific embodiments have been illustrated and describedherein, it is appreciated by those of ordinary skill in the art that anyarrangement which is calculated to achieve the same purpose may besubstituted for the specific embodiments shown. This application isintended to cover any adaptations or variations of the presentinvention. Therefore, it is manifestly intended that this invention belimited only by the claims and the equivalents thereof.

What is claimed is:
 1. A drive system for driving a vehicle over asurface comprising: a flat track having an inner surface and an outersurface; driving lugs attached to the inner surface of the flat track; adriver for driving against the driving lugs, the driver positioned abovethe surface over which the vehicle is driven; a first end axle; a secondend axle; wheels attached to the first axle and the second axle; thedriver, the first end axle and the second end axle fixed with respect tothe flat track such that the flat track is held in substantiallyconstant tension; additional wheels, the wheels and the additionalwheels in contact with the inner surface of the flat track as the flattrack engages the surface, the additional wheels not fixed with respectto the first axle, the second axle and the driver; and an undercarriageand at least one suspension mount, wherein the driver, the first axleand the second axle are fixed in relation to the undercarriage and theadditional wheels are attached to the undercarriage via the suspensionmount so that the additional wheels are not fixed with respect to theundercarriage.
 2. The drive system of claim 1 wherein the suspensionmount comprises a tubular stock having a substantially square crosssection; a bar having substantially square cross section, the length ofthe diagonal of the bar being less than the distance across the insidetubular stock so that the bar may be positioned within the tubularstock; and elastomeric elements positioned between the bar and thetubular stock.
 3. The drive system of claim 1 further comprising anadditional suspension mount, the additional suspension mount forattaching the undercarriage to a vehicle.
 4. The drive system of claim 3comprising a plurality of additional suspension mounts.
 5. The drivesystem of claim 1 wherein the driving lugs on the inner surface of thetrack are aligned, and the wheels are aligned so that the driving lugspass between the wheels in contact with the inner surface of the flattrack.
 6. The drive system of claim 5 further comprising additionalwheels in contact with the inner surface of the track as the trackengages the surface, the additional substantially solid wheels providedsuch that the track provides support between each of the wheels incontact with the track while the track contacts the surface as thevehicle traverses the surface.
 7. The drive system of claim 5 whereinthe wheels are mounted on axles.
 8. The drive system of claim 7 whereineach axle includes at least two wheels.
 9. The drive system of claim 1wherein the driving lugs are formed into two aligned rows on the innersurface of the track, and the plurality of wheels are aligned so thatthe driving lugs pass between the wheels in contact with the innersurface of the flat track.
 10. The drive system of claim 1 wherein thedriver for driving the track is located toward the rear of the vehicle.11. The drive system of claim 1 wherein the driver is located more thanone foot above the ground.
 12. The drive system of claim 1 wherein thedriver further includes a driver sprocket having a plurality ofrotatable sleeves for driving the driving lugs associated with thetrack.
 13. The drive system of claim 1 wherein the driver furtherincludes a driver sprocket that is substantially cylindrical in shapeand has a substantially curved inner portion, the vehicle furthercomprising a scraper positioned near the substantially curved innerportion of the driver sprocket to remove debris from the driversprocket.
 14. The drive system of claim 1 further comprising torsionaxle suspension units attached between the vehicle frame and the wheels.15. The drive system of claim 14 wherein the torsion axle comprises: afirst solid axle portion; a second tubular portion, the first solid axleportion fitting within the second tubular portion; and an elastomericportion fitting within the spaces between the first solid axle and thesecond tubular portion.
 16. The driver system of claim 1 wherein thedriver has a hydraulic motor therein.